Micro-Neutralization Assay – S-IgA (mucosal IgA)

The Micro‑Neutralization assay for Secretory IgA (S‑IgA) is a functional immunological method used to evaluate the neutralizing capacity of mucosal IgA antibodies against viral pathogens, providing critical insight into protective immunity at mucosal surfaces. In this assay, biological samples such as saliva or mucosal secretions containing S‑IgA are serially diluted and incubated with a defined amount of live virus, allowing neutralizing antibodies to bind and inhibit viral infectivity. The mixture is then added to susceptible cell cultures, where any non-neutralized virus can infect and replicate. After an incubation period, viral infection is assessed through cytopathic effect or detection systems, and the degree of inhibition is quantified. Results are expressed as the neutralization titer, corresponding to the highest dilution of sample that effectively prevents viral infection. This assay specifically captures the functional activity of S‑IgA, including its unique role in immune exclusion and pathogen neutralization at mucosal barriers, as described in mucosal immunity studies. The method is widely used in VisMederi to evaluate vaccine immunogenicity and immune protection in respiratory and enteric infections, such as those caused by human metapneumovirus, parainfluenza viruses, human rhinovirus, RSV, Influenza A and B and SARS CoV-2 viruses.